Vertical shaft impact crushers (VSI-crushers) are used in many applications for crushing hard material like rocks, ore etc. U.S. Pat. No. 3,154,259 describes a VSI-crusher comprising a housing and a horizontal rotor located inside the housing. Material that is to be crushed is fed into the rotor via an opening in the top thereof. With the aid of centrifugal force the rotating rotor ejects the material against the wall of the housing. On impact with the wall the material is crushed to a desired size. The housing wall could be provided with anvils or have a bed of retained material against which the accelerated material is crushed.
The rotor of a VSI-crusher usually has a horizontal upper disc and a horizontal lower disc. The upper and lower discs are connected with a vertical rotor wall. The upper disc has an aperture for feeding material into the rotor. The material lands on the lower disc and is then thrown out of the rotor via openings in the rotor wall.
The material exerts an impact force and wear on the lower disc. To ensure a long life of the lower disc it is usually provided with a distributor plate. The distributor plate, which is located at the centre of the lower disc, is made from a material that is resistant to impact and wear.
In U.S. Pat. No. 3,767,127 to Wood a deflection disc assembly is described. The deflection disc has an outer ring and a core member. A central stud passing through the core member and threadedly engaged to the rotor shaft holds the deflection disc in position in the rotor.
U.S. Pat. No. 4,690,341 to Hise describes a flat centre wear plate which is fixed to the rotor shaft by a bolt.
WO 01/30501 describes a distributor comprising a first part having an inclined surface and a second part with a flat surface. A bolt holds the first and second parts fixed to a rotor shaft.
The distributor plates described above do not have a very long life and cause a rather long down time when they need to be replaced. To make it possible for a person working with the rotor to replace the distributor plate it is often necessary to dismantle the top of the rotor.